1. Field of the Invention
The present invention relates to a conveyor chain for use in a crossed delivery conveyor, the crossed delivery conveyor comprising a first conveyor for conveying articles in a first direction and a second conveyor for conveying articles in a direction orthogonal to the first direction, the second conveyor being disposed in abutment against a side edge of the first conveyor.
2. Description of the Related Art
FIG. 8 shows an example of a crossed delivery conveyor. The crossed delivery conveyor, designated by 60, comprises a first conveyor 62 for conveying articles in a first direction and a second conveyor 64 for conveying articles in a direction orthogonal to the first direction. The second conveyor 64 is disposed in proximity to a side edge of the first conveyor 62. In the crossed delivery conveyor 60 of this type, as indicated with arrows in FIG. 8, guides 66 are provided for loading an article A from the first conveyor 62 onto the second conveyor 64 or for discharging an article from the second to the first conveyor.
The first conveyor 62 shown in FIG. 8 comprises conveyor chains 68 and 70 arranged in two lines. In each of the chains 68 and 70, a plurality of links provided with article loading portions are connected together in an endless form. In the chain 68, located on the side closest to the second conveyor 64, each of the links is provided with an overhanging slat 72 extending from the associated article loading portion in a direction orthogonal to the article conveying direction of the chain.
As shown in detail in FIG. 9, the second conveyor 64 is disposed so as to extend under the first conveyor 62 and therefore the overhanging slats 72 are needed for the transfer of articles from the first conveyor 62 onto the second conveyor 64. An article is moved from an article loading portion on the first conveyor 62 to overhanging slats 72 while being guided by the guides 66 (FIG. 8) and is then loaded onto the second conveyor 64 from the overhanging slats 72.
In the conveyor it is desirable that the chain pitch of a conveyor chain be set small. This is because by setting the chain pitch small, it is possible to suppress a polygonal motion of the chain and hence possible to convey articles in a stable manner.
On the other hand, when articles are loaded and discharged on a crossed delivery conveyor, it is preferable that the chain pitch be set large. This is because by setting the chain pitch large, the number of overhanging slats 72 which the article straddle when moving between the first and second conveyors 62, 64 becomes smaller, permitting a stable delivery of the article.
For example, in the case where unstable articles such as petaloid-shaped PET bottles are to be conveyed using the crossed delivery conveyor, it is important that the articles be kept stable not only during the regular conveyance on the constituent conveyors but also during transfer between the conveyors. The relation of the chain pitch to the article stability is not considered at all in the conventional crossed delivery conveyor.
FIG. 10 illustrates the behavior of an article when transferred onto an overhanging slat 72 between the first and second conveyors 62, 64. The overhanging slat 72 is attached to a link in a cantilevered state. When an article A has moved onto the overhanging slat 72, a moment acting to cause tilting of the entire link is exerted on the link.
In the conventional crossed delivery conveyor, rails 74 support links for defining a track of the chain, but no consideration is given about how the load acting on each overhanging slat 72 is to be borne. Therefore, when the article A has moved from the article loading portion to the overhanging slat 72, there is a fear that the load of the article A may cause the chain to tilt and that consequently the article present on the overhanging slat may fall down.
Moreover, in the first conveyor 62, the left-hand conveyor chain 70 and the right-hand conveyor chain 68 with overhanging slats 72 are separate chains, so when the right-hand chain 68 with overhanging slats 72 tilts, there occurs a difference in height at a joint portion between the right and left chains. The article A being moved toward the second conveyor 64 along the guides 66 (FIG. 8) is likely to be caught in such a stepped portion at its bottom and may fall down. Likewise, the article A when straddling the right and left chain 68, 70 is likely to fall down upon tilting of the right chain 68.
Further, the spacing between the conveyor chains of the first and second conveyors 62, 64 is set narrow so that articles can be transferred stably from one to the other conveyor, so if the conveyor chains tilt even slightly, there also arises the problem that the chain 68 of the first conveyor 62 comes into contact with the second conveyor 64.
Further, the crossed delivery conveyor shown in FIG. 8 takes into account only loading articles to, and discharging articles from, one side. In the first conveyor 62, therefore, the left hand conveyor chain 70 in the figure does not function at all as a crossed delivery conveyor. If the article loading and discharging directions are different, it is necessary to substitute a separately manufactured conveyor for the left hand conveyor chain 70. This is very uneconomical.
It is an object of the present invention to provide a conveyor chain capable of stably conveying articles, particularly petaloid-shaped articles easy to fall down such as PET bottles, in a crossed delivery conveyor and also capable of delivering such articles stably between constituent conveyors of the crossed delivery conveyor.
Another object of the present invention is to provide a conveyor chain which prevents tilting of overhanging slats during the delivery of articles between constituent conveyors of a crossed delivery conveyor.
A further object of the present invention is to provide a conveyor chain capable of loading and discharging articles in both right and left directions in a crossed delivery conveyor.
According to the present invention, for achieving the above-mentioned objects, there is provided a conveyor chain for use in a crossed delivery conveyor, comprising a plurality of links connected together in an endless form, the links being each provided with an article loading portion. The links are comprised of first links and second links, the first links being each sandwiched in between two adjacent ones of the second links in a conveyance direction of the conveyor chain to constitute an endless conveyor chain. The first links are each provided with an overhanging slat which extends in a direction orthogonal to the conveyance direction of the conveyor chain from the article loading portion of the first link. The overhanging slat extends also in the conveyance direction of the conveyor chain along a side edge of the article loading portion of the associated second link, and the overhanging slat of each of the first links is adjacent to the overhanging slats of preceding and succeeding ones of the first links.
In a crossed delivery conveyor provided with guides for loading articles from a first conveyor to a second conveyor or for discharging articles from the second to the first conveyor, the conveyor chain of the present invention is used mainly in the first conveyor.
For example, in case of loading articles from the first to the second conveyor, the articles are in a loaded state onto article loading portions of constituent links in the conveyor chain of the first conveyor. As the conveyor chain is operated, the articles are conveyed in the conveyance direction of the first conveyor. At this time, a velocity component of the articles lies in only the conveyance direction.
In case of loading an article onto the second conveyor at an intermediate position of the first conveyor, the article moves along a guide. At this time, on the first conveyor the article moves with two velocity components in both conveyance direction and a direction orthogonal thereto.
When an article present on any of the first links moves in a direction orthogonal to the conveyance direction, it moves from the article loading portion on the first link to an overhanging slat of the first link. When an article present on any of the second links moves in a direction orthogonal to the conveyance direction, it moves first to an overhanging slat of the associated first link from the article loading portion on the second link. Thereafter, both articles are loaded onto the second conveyor. Thus, the article loaded on the first link and the article on the second link each move onto an overhanging slat of the first link and thereafter loaded onto the second conveyor.
The pitch of the conveyor chain is determined by a uniform pitch of all the links including the first and second links. On the other hand, the pitch of the overhanging slats is determined by the pitch of the first links provided with the overhanging slats.
For example, in a conveyor chain having first and second links arranged alternately, the pitch of overhanging slats is twice as large as the chain pitch. For example, in a conveyor chain wherein each of first links is disposed at every two second links, the pitch of overhanging slats is three times as large as the chain pitch.
As noted earlier, for suppressing a polygonal motion of the chain and conveying articles stably, it is preferable that the chain pitch be set small. On the other hand, in case of loading and discharging articles in a crossed delivery conveyor, it is preferable that the pitch of a chain provided with overhanging slats be set large. In the present invention, the pitch of only overhanging slats can be changed to twice, three times, . . . of the chain pitch without changing the chain pitch. As a result, when an article is loaded or discharged between the first and second conveyors, the number of overhanging slats which the article straddle becomes smaller, thus permitting a stable delivery of article between the conveyors.